The combination of a male luer connector with a female luer member is widely used in the medical field to connect two fluid conduits end to end. Such male/female sets are employed to join hypodermic needles to syringes and one catheter to another catheter, for example, in order to provide liquid leakproof and mechanically secure connections. A luer connection comprises two distinct elements, a tapered fitting called a "luer-slip" and a subordinate fitting to add additional strength to the connection. The subordinate fitting is generally a "luer-lock" threaded fitting.
The first element, the luer-slip fitting, involves the mating of a conical male nozzle member with a conically-hollowed female socket member. Both members are also hollowed axially to provide communication of the fluid passage between them. The tapers of the two cones are similar, so that, upon slipping the conical male nozzle member into the conically-hollowed female socket member, a frictional seal is achieved which is substantially fluid-tight. The conical tapers of the two members are prescribed by an industry standard, which sets the "luer taper" for such fittings.
The second aspect of a luer taper connection is a subordinate fitting, commonly a threaded connection, between the male and female members which engages to establish an axial force tending to maintain the frictional seal established by the slip fitting. Typically, the male taper member has a coaxial cylindrical skirt which carries internally one component of the threaded connector, while the female taper member carries the other part of the threaded connector externally. The female member may carry a full thread but, more commonly, only an abbreviated thread, in the form of a pair of lugs, is provided. This type of threaded fitting is called a "luer-lock" fitting.
The American National Standard Institute (ANSI) first proposed an American National Standard in 1955 to make luer slip fittings and luer-lock fittings uniform from manufacturer to manufacturer. ANSI MD70.1-1955 was subsequently adopted by the industry. Thus, individual luer fittings for use in medical device applications can make leakproof and mechanically secure connection with any other available individual mating luer fitting. At the time the standard was written the luer taper dimensions required a cone 4.318 mm in diameter at the large end, 3.937 mm in diameter at the small end and 6.350 mm in length, i.e., a 6% taper. In 1955, luer taper fittings were generally made of rigid glass or metal, but semi-rigid thermoplastic fittings of polycarbonate, polypropylene, etc. now predominate.
With reference to semi-rigid luer taper fittings, according to a proposed revision of the 1955 ANSI Standard, the diameter of the small end of the male nozzle member must lie in the range 3.925-4.027 mm, and the minimum length of the nozzle must be 7.500 mm. The diameter at the large end of the female socket member must lie in the range 4.270-4.315 mm, and the minimum depth of the socket must be 7.500 mm. The minimum length of engagement between the male nozzle and the female socket must be 4.050 mm. The Standard also provided requirements for luer-lock fittings, such as the root and crest diameters for the thread, thread pitch and thread angle, but the proposed revision technically applied only to rigid materials. The thread is generally a 1.5 turn, 0.25 inch advance thread of a rather crude design. The most recent Standard is ANSI MD70.1-1992. Reference to the most recent revision of the ANSI Standard should, of course, be made when any new luer taper fitting is being designed.
Whereas the adoption of industry standards for luerslip and luer-lock fittings has encouraged the use of such connectors, their use is not free from problems. Such problems include fluid leaks due to mismatching of the sealing edges, cross-threading and thread stripping. Whereas the ANSI Standard provides certain dimensions for luer slip fittings, dimensions appear as ranges, and variations between manufacturers within those ranges lead to misfits and leakage. Cross-threading of luer-lock fittings generally occurs when excessive force is applied upon thread engagement, or the members of the fitting are misaligned as the threads are engaged. The result is uneven mechanical force applied to the luer slip fitting and possible leakage thereof. The threads in a luer-lock fitting can be stripped by overzealous application of force upon connection and can lead to misalignment and fluid leakage as the fitting is engaged and disengaged several times, with increasing damage to the threads and slip fit.
Another set of problems arises because the luer taper fittings of metal, glass or thermoplastic, materials believed to be necessary because of the frequent engagement, disengagement and rough handling they receive, are often used to connect soft, resilient elastomeric cathether materials, typically made of silicone rubber. These connections are usually made with an adhesive. Unless great care is taken to smooth the transitions from one material to the other, sharp steps and cavitations are often present in the resultant cathether terminated with a luer taper fitting. These steps and cavitations tend to collect material from the fluid passing through the connected conduits, and the residue is nearly impossible to flush out. This residue is known to be responsible for partial occlusions and infections. The abrupt transition in materials can also be the cause of thrombus formation when blood is transported through the conduits.
It is to the solution of the aforesaid problems that this invention is directed.